How to improve Cycles Render times on a model Space Craft?
When using the GPU, blender actually renders fast with larger tile size: 

There is an addon called auto tile size that will configure this for you. (It can be found in File > User Pref > Add-ons > Auto Tile Size ). If you would rather tweak it manually you can find the tile size in the performance section in the render tab.

Another thing you can do is turn down the bounces and turn off caustics. (These are found in the light path section in the render tab). I would turn down light bounces a lot especially because there is only one light source.

Happy Rendering!

Sources: BlenderGuru